svelte/test/runtime/samples/lifecycle-after-flush/main.html

<script>
	import { afterFlush } from 'svelte';

	export let snapshots = [];

	let count = 0;
	let button;

	function click() {
		count += 1;
		snapshots.push(`before ${button.textContent}`);

		afterFlush(() => {
			snapshots.push(`after ${button.textContent}`);
		});
	}
</script>

<button bind:this={button} on:click={click}>{count}</button>